1. Field of the Invention
The present invention relates to a technique in which a plurality of pieces of video data to be synthesized and output is transmitted to a plurality of devices, thereby synthesizing and outputting the data.
2. Description of the Related Art
There is a system in which a plurality of pieces of divided video data is projected by using a plurality of projectors and a projectional image is synthesized therewith to display large screen video thereof, a system in which a plurality of images of projectors having insufficient luminance is overlapped with one another to display an overlapped image, and a system in which a right image and a left image overlap each other to display a three dimensional (3D) video. As screen sizes have increased, the distance between a projector and video source apparatus has increased, which has resulted in a demand for wireless video data transmission systems to overcome the issue of running wires over the increased distance.
In order to perform stable data transmission between nodes connected to each other via a wireless communication path, there is a method in which a plurality of pieces of data having different levels of detail is generated from a single piece of data to transmit the generated plurality of pieces of data. For example, Japanese Patent Laid-open Publication No. 2000-78116 discusses a transmission device that generates a high quality signal and a low quality signal based on a single piece of broadcasting digital data and transmits the generated signals differently-timed and a reception device that receives the high quality signal in a normal reception mode to reproduce the signal and receives the low quality signal in a fault mode to reproduce the signal.
Japanese Patent Laid-open Publication No. 2004-32604 discusses a transmission device that separately transmits a plurality of pieces of data generated from a single piece of information but having different compression ratios by using a plurality of transmission channels having different transmission rates and a reception device that switches the transmission channels to be used based on an error rate of the transmission channel in receiving the data. Japanese Patent Laid-open Publication No. 2010-213190 discusses a transmission node that transmits uncompressed video data by using a high speed transmission channel and transmits compressed video data by using a low speed transmission channel, respectively, and a reception node that reproduces the uncompressed video data when a high speed transmission channel can receive the data and reproduces the compressed video data when the high speed transmission channel is blocked, respectively. Japanese Patent Laid-open Publication No. 2010-213191 discusses a transmission node that transmits compressed video data by using a low speed transmission channel and transmits loss data that misses during the compression of the video data by using a high speed transmission channel, respectively, and a reception node that reproduces video by synthesizing data produced by decompressing the compressed video data with the loss data.
However, with the conventional technique, in a case of a wireless multi-projection system where video data is transmitted to each of a plurality of destination nodes connected to projectors, video quality of video data output from each destination node is difficult to homogenize. For example, in a case of a system in which a single piece of video is divided into right video, left video, upper video, and lower video to transmit the plurality of pieces of video, if the video qualities in all the pieces of the divided video are not homogenized, a low quality video disturbance can occur that affects the quality of the video being displayed. Specifically, in a case where an object contained in video, such as scenery or a person, lies astride the left video and the right video, a difference in video quality between the right video and the left video becomes remarkable. Further, in a case of providing edge blending processing such that portions of the plurality of pieces of the divided video overlap with one another to adjust a luminance of joint between the video and the video so as not to make the joint imperceptible, if the plurality of pieces of video having different qualities overlap one another, the joint becomes rather remarkable. Also, in a case where the plurality of pieces of video overlap with one another in order to improve 3D video and a luminance thereof, if high quality video and low quality video overlap each other, a disturbance of the low quality video becomes remarkably visible and thus a degradation of video quality in its entirety becomes remarkable.